In a vehicular lighting in which light from semiconductor light-emitting elements is vertically diffused by a vertical diffusion part when entering an incident surface of a projection lens and a cut-off line in a light distribution pattern is vertically diffused and dimmed for the purpose of improving visibility of a driver, optical streaks (optical spots) are sometimes formed on a road surface.
To solve such a problem, Patent Literature 1 discloses a vehicular lighting that includes a light source and a lens that externally irradiates light from the light source as a light distribution pattern having a cut-off line. A diffusion part for diffusing incident light is formed on an incident surface of the lens. The diffusion part is formed by crossing continuous minute concave curved surfaces or minute convex curved surfaces (see Patent Literature 1).
In the vehicular lighting disclosed in Patent Literature 1, the diffusion parts are formed on the entire incident surface (the entire surface corresponding to the range contributing to forming a light distribution pattern) of the lens without any gaps.